For the past few weeks, I’ve been learning and expanding my knowledge of the CQRS pattern. Under the guidance of Mr. Peter, I have been steadily progressing in my understanding of CQRS. This week, my focus was on implementing the final components of the pattern: the “Get by Id” and “Get List” functionalities for an entity.<\/p>\n\n\n\n
First, I created the Get List Query Handler class. This class implements the IRequestHandler interface and is responsible for handling the query to retrieve a list of entities. It utilizes the IMapper and a specific service interface. Then, within the Handle method, I first check if the search name provided in the query is null and assign an empty string if necessary. This allows for more flexible search functionality. Next, I call a service to read the paged entity based on the search criteria and pagination details provided in the query.<\/p>\n\n\n\n
To prepare the response, I use AutoMapper to map the retrieved list of entities to a list of the entity Dto objects. Additionally, I fetch the total count of entities that match the search criteria to assist with pagination. Finally, I return a PagedDto object containing the count, the mapped list, and the page and size information from the query. <\/p>\n\n\n\n
Moving on to the Get Query By Id Handler class, which handles the query to retrieve a specific entity by its ID. Similar to the previous handler, it implements the IRequestHandler interface and relies on the IMapper and service interfaces. Inside the Handle method, I perform validation using the Get Query Validator. If any validation errors occur, I throw an InvalidOperationException with the corresponding error messages. Otherwise, I proceed to retrieve the entity using the service based on the supplied Id in the query. If an entity is found, I map it to the Dto using AutoMapper and return the result. However, if the entity is not found, I return null to indicate that no entity with the specified ID exists.<\/p>\n\n\n\n
To ensure the correctness of my implementation, I have also included a couple of unit tests. These tests verify the success scenarios for both the Read By Id and Read List methods. They utilize a client to simulate HTTP requests and check the returned status codes and data.<\/p>\n\n\n\n
In addition to the query handlers and tests, I have also expanded my knowledge by implementing another implementation of the service interface. This interface serves as the abstraction for fetching entities based on various criteria, and I made sure to create the methods in asynchronous form as advised by Mr Peter.<\/p>\n\n\n\n
The added methods in the service interface provide the flexibility to retrieve entities by ID, search name, and pagination. For example, the ReadByIdAsync method accepts an ID as a parameter and fetches the corresponding entity asynchronously. It utilizes the underlying data access layer, to retrieve the entity. Similarly, the ReadPagedByAsync method takes parameters such as a search name, page number, and page size to perform a paged retrieval of entities based on the search criteria. <\/p>\n\n\n\n
Overall, by implementing these methods in an asynchronous manner, I ensure that the retrieval operations can be performed efficiently and non-blocking. This enables better scalability and responsiveness in the application, especially when dealing with a large number of entities or concurrent requests. Moving forward, my next task involves delving into the UI aspect, where I will embark on learning about WPF, MVVM, and Prism.<\/p>\n\n\n\n
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For the past few weeks, I’ve been learning and expanding my knowledge of the CQRS pattern. Under the guidance of Mr. Peter, I have been steadily progressing in my understanding of CQRS. This week, my focus was on implementing the final components of the pattern: the “Get by Id” and “Get List” functionalities for an … <\/p>\n